This is a revised application for an ancillary study to the Women's Health Initiative (WHI) at Wayne State University's Clinical Center that would investigate whether there are ethnic differences in cross-sectional geometry and gross morphology (i.e., bone architecture) of the proximal femur. The investigators will focus on the cross-sectional aims of the previous application and postpone longitudinal studies (i.e., the effect of hormone replacement on morphology) until appropriate pilot data are available. This study will complement and enhance, but not duplicate, the objectives of the WHI's bone density components by providing morphometric data that would not otherwise be available. The study cohort (n=400, 60% African-American and 40% White) will be recruited from among the 1083 subjects expected to participate in WHI's hormone replacement therapy (HRT) trial in Detroit. The investigators propose to obtain hip x-rays and a proximal femur measurement by dual-energy x-ray absorptiometry (DXA) before the subjects are randomized to treatment. They will then apply new analytical approaches to the radiographic and DXA data in order to address the following specific aims: 1) to identify significant ethnic (African-American/White) differences in the following: femoral cortical thicknesses; head diameter; neck-shaft angle; diaphyseal breadth; hip axis length; and Singh Index (grades of trabecular loss), from hip x-rays; and 2) to identify significant ethnic differences in cross-sectional structural geometry of the femoral neck based on "Hip Structure Analysis" of DXA data. The investigators state that the significance of the proposed epidemiologic study is that, at present, essentially nothing is known about the influence of ethnic background on proximal femoral morphology other than bone mass. They state that the data would provide a basis for evaluating the merits of a future study of whether ethnic differences in architecture contribute to ethnic differences in hip fracture. They further state that the research question is also of clinical significance, since the objective is to identify measures of bone architecture that could be used in addition to bone mass for the critical evaluation of therapies for osteoporosis (such as HRT).